port size

pi r^2 to find the area of a circle

• pi is 3.14
• r is radius, or half the diameter of a circle
• ^2 is squared, or the number times itself
• pi r^2 is 3.14 X the result of radius squared
• pi r^2 gives you the square inches of a circle

You want to change the shape of the opening but keep it the same square inches.  The length of the port is not a factor and you will leave it exactly the length it already is.

• Find the square inches of your circle using pi r^2 (ex. a 6 inch diameter circle yields 28.26 square inches)
• Decide on the longest side you want your square or slotted port opening to be
• Divide the total square inches of the circle by that long side, in inches (ex. 28.26 / 11.5 = 2.46)
• The result is the measurement of the shorter side of the port opening

In the example, the 6" round port equals a slotted port 11.5 X 2.46 inches.  Round measurements to the nearest Imperial or metric value.  2.46 would be  2 7/16 to 2 1/2.

You should keep the ratio of length to width of the slotted opening at no greater than 8:1.